This invention relates generally to fuel gas distribution and metering, and more particularly to local distribution of fuel gas to multiple points of use, with gas consumption by each user separately metered for readout at a remote location.
In providing fuel gas utility service to multiple users in a single structure, such as residential units in an apartment or condominium building, it is desirable to individually meter gas consumption for each unit. Formerly, it was common practice to use a single meter on the main infeed gas line serving all of the units and to divide the charges equally among the units. This practice is now disfavored. It is not conducive to conservation and can unfairly overcharge frugal users to the undeserved benefit of those who use more gas.
As shown in FIG. 1 of the drawings, more modern practice provides for separate metering of each unit. Conventionally, it is done by dividing the main infeed gas line into branch lines outside the structure; installing separate meters in the branch lines at a single location, typically outside the building; and plumbing each unit individually for gas service. This approach to gas distribution and metering has several drawbacks.
First, conventional gas meters are positive displacement, mechanical devices which measure gas usage directly and are cumbersome and expensive. For easy reading and ventilation, to minimize the dangers of gas leakage, such meters are typically located outside the building which they serve. Ambient temperature variations over a wide range introduce small, but significant, measuring inaccuracies, necessitating use of temperature compensation means in such meters to minimize the inaccuracies. Other methods which have been proposed for directly measuring gas consumption--measurement of differential pressure or gas velocity through an orifice--are even more expensive and more prone to inaccuracy.
A second drawback is the cost of individually plumbing each unit for gas service. This cost is especially burdensome when retrofitting buildings originally equipped with a single meter for several units. Accordingly, it would be desirable to devise a fuel gas distribution and metering system which safely provides for separate metering of each unit, using inexpensive and highly accurate metering apparatus, but does not require running separate piping from outside the building into each unit. Heretofore, such a capability has not been available to the gas utility industry.
In fields other than fuel gas distribution, a variety of devices have been proposed for measuring flows or discharges of fluids. However, none meets the foregoing needs of the gas utility industry.
U.S. Pat. No. 2,018,538, to Webb, proposes a liquid measuring apparatus to indicate the amount of liquid draining from a constant level tank through a fixed orifice during a period of time indicated in gallons by a clock. The clock is mechanically coupled to, and actuated by, a linkage controlling the opening and closing of a valve in the orifice. U.S. Pat. No. 2,428,383, to Prangley et al., discloses a gasoline pump in which a speed regulator controlled by a valve maintains the flow of gasoline through the dispensing line at a constant rate. A pressure-sensing device senses gas flow to initiate metering of the gasoline by a mechanical metering device.
U.S. Pat. No. 3,020,749, to Cropper et al., discloses a viscosimeter for electronically measuring the amount of time required for a quantity of a fluid to drain from a capillary tube. The elapsed time is multiplied by a constant to produce a measure of viscosity. This device includes a binary counter comprising an oscillator and binary dividers connected to a counter indicator.
U.S. Pat. No. 3,666,143, to Weston, discloses a system for dispensing predetermined-volume units of beer from several beer taps, and includes a pressure-sensing device in its electrical circuitry to normalize the flow at different pressures. Manual operation of the beer tap initiates timing of a predetermined interval during which beer is dispensed. The total number of units of beer dispensed from each tap is electronically counted. U.S. Pat. No. 4,225,057, to Horn, also discloses a beer-dispensing monitor, which mechanically senses the flow of beer from the tap and measures the quantity of beer dispensed at a predetermined flow rate, by using a timer to time the duration of flow. U.S. Pat. No. 4,278,186, to Williamson, discloses a liquor-dispensing and monitoring device to control the volume of liquor dispensed in each unit from a liquor bottle. A tilt switch in the bottle cap actuates timer circuitry in the device whenever a drink is poured. Monitoring data is radio-transmitted to a remote receiver and computer, which counts the number of drinks dispensed from each bottle.
All of the foregoing devices deal with the measurement of liquid discharges over time. However, none of them pertains to the distribution and metering of fuel gas. More particularly, none addresses the problems faced by gas utilities in economically providing gas distribution services to multiple points of use, separately metering consumption of fuel gas by each user, and providing meter data for readout at a convenient location remote from the point of use of the gas. Accordingly, there remains a need for an improved fuel gas distribution and metering system.